Au contraire. A big part of the warrior class identity is effectively gaining health (armor cards) and using health (weapons). This card offers an interesting way to gain a health bonus while providing some other effect. It's by no means an auto-include, and that means you have to think carefully about how much your deck wants armor when deciding whether you want to include this card.

Although Tower Shield +10 is likely the worst outcome, it is simultaneously the most interesting. The person running the card needs to be able to leverage their health much more than usual should they draw the +15 armor card, and the person playing against it needs to consider whether they should play around a huge injection of armor. (Because an Unidentified Shield only has a 25% chance of being Tower Shield +10, not playing around is punished less often... but in some cases you won't want to take the risk.)

Generally just gaining armor isn't very valuable, however Tower Shield +10 is actually pretty good only because it gives such a huge amount. You're playing against a face deck and suddenly you gain 15 armor, and you can run two of these. Also good against most combo decks.

But unless you're able to follow up with a board clear, you just delayed losing by a turn. You pay 6 mana, and do nothing to your opponent. The other effects allow you to kill a minion or generate a board that can help you fight against their minions.